Diarrheal illnesses represent a major cause of morbidity in Puerto Rico. The results obtained previously suggest that Vibrio spp. may be the etiologic agent for a portion of the reported outbreaks. In an attempt to establish the importance of vibrios as agents of such illnesses in Puerto Rico, the objectives of the proposed study are: 1) to determine the presence of pathogenic and other halophilic Vibrio spp. in market level seafoods sold in Puerto Rico; 2) to determine the presence and distribution of pathogenic and halophilic Vibrio spp. in tropical coastal and estuarine waters in Puerto Rico and; 3) to train several students in food and water microbiology techniques. Seafood samples will be purchased rom local vendors and analyzed for aerobic plate count APC total and fecal coliform levels, and the presence of pathogenic, halophilic Vibrio spp. Samples will be plated onto thiosulfate-citrate-bile salts-sources (TCBS) and cellobiose-polymyxin-colistin, (CPC) agars to determine the presence of the organisms. Water samples obtained from sea and estuarine source which are used as shellfish harvesting points will be analyzed in situ for salinity, pH and temperature, and for APC, total and fecal coliform levels and total vibrio count. In addition, water samples will be plated onto TCBS and CPC agars in order to isolate Vibrio spp. The Vibrio isolates obtained will be characterized both biochemically and serologically using conventional techniques. Two to dour undergraduate students will be recruited to assist the PI during the period covered by the proposal.